The subject matter disclosed herein relates to methods of treating intervertebral disc degeneration (IVDD) and, in particular, to the use of hydrogels as a nucleus pulposus (NP) tissue replacement. IVDD is the most common diagnosis for lower back pain, a debilitating condition that annually affects 15-30% of the United States population, with associated annual costs of $194 billion. Typical conditions arising from IVDD include disc herniation, degenerative spondylolisthesis, spinal stenosis and degenerative disc disease. These conditions result from a complex combination of aging, trauma and unhealthy lifestyles. Discectomy, which involves removal of NP tissue, is employed when non-operative treatments fail to alleviate pain. Although discectomy often provides immediate pain relief, it does not restore disc biomechanical function due to loss in disc height and intradiscal pressure. Lumbar discectomy is the most common surgery for herniated discs, during which portions of the NP are resected to decompress affected nerve roots. However, this treatment has a high recurrence rate (5-15%), and frequently requires secondary intervention. Additionally, the void space caused by NP removal leads to lower disc height, and subsequently more back pain. For heavily degenerated discs, spinal fusion is typically used, however, altered load distribution over time produces damage to adjacent discs. Thus, current treatment options have been inadequate for long-term disease management.
NP replacements have been explored in order to avoid long-term complications post discectomy. Several acellular biomaterials have been commercially produced in the past decade, but have not necessarily advanced beyond the developmental stage or received Food and Drug Administration (FDA) clearance for use in the United States. Although these NP replacements have been shown to redistribute loads and are less invasive than total disc replacements, several complications have been reported. These include extrusion of the material through the annulus, wear debris, and fatigue or fracture failure of cartilaginous endplates. Also, most of these materials fail to conform to the unique geometry of the NP and do not support cell encapsulation. For example, in vitro characterization of photocrosslinked methacrylated carboxymethylcellulose (CMC) hydrogels demonstrated that these materials possess functional properties comparable to native NP and support stem cell differentiation towards an NP phenotype. A recent advance employed redox crosslinking, thereby providing an important step in the development of an injectable CMC hydrogel formulation amenable to clinical translation. However, injection of the CMC/redox initiator mixture into large bovine motion segments resulted in extravasation of the polymer solution and limited polymerization within the disc. Thus, improved hydrogel formulations are desired to enable stable polymerization.
The discussion above is merely provided for general background information and is not intended to be used as an aid in determining the scope of the claimed subject matter.